Mechanical pencil

ABSTRACT

A mechanical pencil, especially for thin leads, wherein a lead supported in a small diameter lead support tube carried by a slide member axially movable in a front part of a tubular housing may be advanced by axial pressure on an actuating member projecting from the rear end of the housing and actuating a collet engaging a rear portion of the lead.

United States Patent 1191 Katz 1 ay 28, 1974 [5 MECHANICAL PENCIL 3,728,033 4/1973 Sonokichi et al. 40l/67 [75] Inventor: Otto Katz, Schwbach, Germany [73] Assignee: A. W. Faber-Caste, Nuernberg', primary Examiner Lawrence Charles Germany Attorney, Agent, or FirmMichael S. Striker [22] Filed: Dec. 4, 1972 [2]] Appl. No.: 312,117

[30] Foreign Application Priority Data [57] ABSTRACT Dec. 4, 1971 Germany 2160306 A mechanical pencil, especially for thm leads, wherein 52 us. Cl. 401/65, 401/67 a lead Supported in a diameter lead PP tube 51 1111.0 B43k 21/16, B43k 21/22 Carried by a Slide member axially movable a from [58] Field 01 Search 401/65-67 P11rt of a tubular housing may be advanced by axial 401/58, pressure on an actuating member projecting from the rear end of the housing and actuating a collet engag- 5 References Cited ing a rear portion of the lead.

UNITED STATES PATENTS 3,724,960 4/1973 Hashimoto et al 401/67 8 Claims, 3 Drawing Figures 1 L 1' li rt 1 2a /2 :5

,2; /0 2a 27 a 4 /2 24 2 /4 /5 a PATENTEDMY 28 m4 sii r l MECHANICAL PENCIL BACKGROUND OF THE INVENTION The present invention relates to mechanical pencils, especially for thin leads, in which the lead is supported in a smaller diameter lead support tube carried by a slide member axially movable in a front portion of a tubular housing and in which the lead may be advanced in axial direction by axial pressure on an actuating member projecting from the rear and of the housing and actuating a collet or clamping mechanism adapted to engage a rear portion of the lead.

In mechanical pencils using thin leads a very exact guiding of the lead over the whole length thereof is necessary in a position of use of the lead in which a rear portion thereof is clamped by the collet as well as in the retracted position of the lead during storing of the pencil. It is further necessary to properly support the lead while the length of the lead changes during the use thereof, whereby the lead support must be axially movable with regard to the elongated housing of the pencil so as to conform with the varying length of the lead. Mechanical pencils with thin leads are especially advantageous for drawing purpose since a sharpening of the lead is in this case not necessary.

A mechanical pencil is already known in which the pencil, during use, abuts not only with the free end of the lead against the writing or drawing surface, but also with a rounded side face provided with a thickened portion in such a manner, that by pressure on the aforementioned surface, a tube for guiding the lead. is pushed into the housing of the pencil so that the lead will project further from the tube. In this way an advance of the lead is possible without interrupting the writing or drawing. The enlargement at the free end of the lead support tube is provided in order to assure that the lead assumes at all time its correct position, that is that the lead will not project beyond the supporting tube to an extend which may cause breakage of the lead during use, but that the lead will sufficiently project beyond the support tube to permit proper writing or drawing.

The enlargement at the tip of the support tube has, however the disadvantage, that when the pencil is used in combination with a straight edge for drawing purposes, the enlarged tip will prevent a perfect guiding of this tip on the straight edge, especially if the pencil is held at differently inclined positions.

Another mechanical pencil is known in the art in which a slide member projecting beyond the front portion of the pencil housing is guided in axial direction of the pencil and connected to a lead advancing mechamm. In this pencil a lead support tube which is connected to the slide member is pushed back according to the use of the lead under the influence of the prssure. The advance of the lead isaccomplished by means of a collet cooperating with a clamping ring which is fastened to a body within the pencil housing and movable between two stops. This construction has a great number of components, which necessarily have to have-very small dimensions, and this construction is therefore rather expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mechanical pencil, especially for thin leads, in which I the lead is properly supported during its use and can be It is an additional object of the present invention to provide a mechanical pencil of the aforementioned kind which is composed of relatively few and simple parts so that the pencil may be manufactured at reasonable cost and will stand up properly under extended use.

With these and other objects in view, which will become apparent as the description proceeds, the mechanical pencil according to the present invention mainly comprises an elongated tubular housing, a guide bushing in the housing, a tubular clamping member axially guided in the guide bushing and having an annular flange at one end and spaced from said one end an increased diameter portion projecting beyond the guide bushing and provided on its free end with an inner conical face, a lead receiving tube axially guided in the tubular member, a collect connected at one end to the lead receiving tube and having at the other end thereof an outer conical face adapted to cooperate with the inner conical face of the tubular clamping member for clamping a lead in the collet, a tubular slide member guided on its inner surface on the outer surface of the portion of increased diameter of the tubular clamping member and, on its outer surface, on the inner surface of the tubular housing, the slide member projecting with one end beyond one end of the housing, a lead supporting tube carried by the slide member and projecting beyond the one end thereof, an actuating member projecting beyond the other end of the housing and connected to the lead receiving tube for movement with the latter in axial direction, and biasing means biasing the actuating member in a direction so as to cause engagement between the outer conical face of the collet with the inner conical face of the tubular clamping member.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. -1 is an axial cross-section through a mechanical pencil according to the present invention and showing the slide member in retracted position;

FIG. 2 is an axial cross-section through the pencil and showing the slide member in advanced position and the collet in open position; and

FIG. 3 is a partial axial cross-section through the pencil showing the slide member in advanced position and the collet in closed or gripping positionf DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1 the mechanical pencil according to the present invention comprises tubular housing means composed of a tubular housing rear part 1 and a tubular housing front part 2 having a slightly conical outer surface. The two parts abut with adjacent ends each other and are provided in the region of the adjacent ends with inner screw threads. The two housing parts 1 and 2 are connected to each other at the abutting ends by means of a guide bushing 3 provided at its outer surface with an outer screw thread threadingly engaged with the inner screw threads of the housing parts 1 and 2. The bushing 3 has a thin walled coaxial annular extension 4 which engages with a close slide fit a non-threaded inner surface portion of the front housing part 2 to properly centralize the latter with respect to the bushing. A tubular slide member 5 is slidingly guided on the inner surface of the front housing part 2 with a frustoconical portion of the slide projecting beyond the free end of the housing part 2. A small diameter lead support tube 6 is coaxially fastened in any convenient manner in the projecting portion of the slide member 5 and a friction ring 8 is coaxially pressed into a cavity of the slide member rearwardly of the lead support tube 6 for frictionally engaging a lead 7 extending through the tube 6. In order to limit axial movement of the slide member 5 outwardly of the housing part 2, the slide member is provided at its inner end with an annular radially outwardly projecting flange 9 adapted to cooperate with an inner shoulder 2' on the housing part 2. A clamping tube or tubular clamping member 10 is axially guided in the guide bushing 3. The clamping tube 10 has at its rear end, facing away from the free end of the housing member 2, a stop flange 11 projecting radially outwardly a small distance beyond the outer surface of the clamping tube 10. The clamping tube 10 has a portion 13 of increased outer diameter projecting in axial direction beyond the guide bushing 3 and forming with the remainder of the clamping tube a shoulder adapted to engage an end face 27 of the guide bushing so as to prevent movement of the clamping tube 10 in upward direction, as viewed in FIG. 1, relative to the guide bushing 3, whereas the flange 11 on the inner end of clamping tube 10 prevents movement of the latter in downward direction by engaging the opposite end face 28 of the guide bushing 3. The clamping tube is provided in the region of its flange 11 with a plurality of axially extending slots so that the flange 11, during assembly, may be compressed to a diameter lightly smaller than the bore in the guide bushing, permitting thereby assembly of the clamping tube with the guide bushing. The'clamping tube 10 is provided at the free end of its large diameter portion with an inner frustoconical face 14. The tubular shaft 16 of a collet 15 is axially movable in the tubular clamping member 10, and the collet 15 has an outer conical face adapted to cooperate with the inner conical face at the end of the tubular clamping member 10. The shaft 16 and the collet 15 are in the usual manner provided with longitudinally extending slots 23. The shaft 16 is releasably connected at its end opposite to the end carrying the collet 15 with one end of a lead receiving tube 17. A tubular lead chamber 18 is connected to the other end of the lead receiving tube 17 and the lead chamber is closed by an actuating button 19 releasably connected thereto and projecting beyond the free end of the housing part 1. An insert 20 fitted into a cavity of the actuating button 19 carries a cleaning wire 21.

A coil compression spring 22 is arranged about the lead receiving tube 17 and abutting with opposite ends thereof against the chamber 18 and the end face 28 of the guide bushing 3.

The above described pencil will operate as follows:

By exerting axial pressure onto the actuating button 19, the collet 15 is moved against the force of the spring 22 toward the lead support tube 6. During such movement the tubular clamping member 10 is taken along until the stop flange 11 engages the end face 28 of the guide bushing and, during further movement of the collet 15, the outer conical face thereof will become axially displaced from the inner conical face 14 of the tubular clamping member 10 so that the collet 15 will open. During further inward movement of the actuating button 19, the collet will abut with its end face against the inner end face of the friction ring 8 and move thereby the slide member 5 in axial direction outwardly of the housing member 2 to the position as shown in FIG. 2 in which the flange 9 on the inner end of the slide member 5 engages the shoulder 2' on the housing part 2. During such movement, the lead is advanced by means of the friction ring 8 so that the slide member 5 and the lead 7 are brought into writing position. After the actuating button 19 is released, the latter, the lead chamber 18, the lead receiving tube 17 and the collet 15 are returned by the action of the compression spring 22 to the position shown in FIG. 1, whereby the collet 15 engages with its outer conical face the inner conical face 14 of the tubular clmaping member 10 and moves the latter likewise until the shoulder on the tubular clamping member engages the end face 27 of the guide bushing 3. Subsequently thereto, the outer conical face of the collet 15 is pressed against the inner conical face 14 under the action of the compression spring 22 so that the collet clamps the lead 7. The pencil is now ready for operation.

A second pressure on the actuating button 19 in the position of the slide member 5 and the tubular clamping member 10 as shown in FIG. 3 will provide an advance of the lead 7. This advance is limited in this case by the distance of the stop flange 11 from the end face 28 of the guide bushing and the lead 7 will thus project beyond the outer end of the lead support tube 6 only for a short distance so that breakage of the lead during writing or drawing will positively be prevented.

The lead 7 is supported during writing or drawing by the lead support tube 6 so that a breakage of the lead will be positively prevented. As the lead during opera tion of the pencil is used up, the slide member 5 which carries the lead support tube 6 is moved inwardly into the housing part 2, and the lead may be used up until the flange 9 on the slide member 5 engages the end face 27 of the guide bushing 3. After this condition has been reached, the actuating buttom 19 has to be pressed again in order to advance another portion of the lead.

The mechanical pencil according to the present invention will assure that the slide member and the support tube 6 thereon will always project beyond the free end of the inner housing part 2. Therefore, the same conditions will be maintained until the portion of the lead projecting beyond the free end of the support tube is completely used up, which is especially important during use of the pencil in connection with a straight edge. The advancing mechanism can be actuated in any position independent from the movement of the slide member. When the housing part 2 is removed from the housing part 1, the advancing mechanism can be checked in a very convenient manner to ascertain any possible malfunction thereof. By positioning the stop flange 11, which accomplishes release of the collet, on the rear end of the tubular member 10, the diameter of the whole advancing mechanism can be held very small while nevertheless assuring a proper clamping and release of the collet. A perfect function of the mechanical pencil is assured by guiding the tubular clamping member in the relatively long bore of the guide bushing, which in turn is properly centered in the front part of the housing by means of the axially extension "of the guide bushing.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of mechanical pencil differing from the type describes abovej While the invention has been illustrated and described as embodied in a mechanical pencil for a thin lead with an axially movable actuating mechanism for advancing the lead, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without deoarting in any way from the spirit of the present invention.

Without further analysus, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. A mechanical pencil, especially for thin leads, comprising, in combination, elongated tubular housing means; a guide bushing in said housing means; a tubular clamping member axially guided in said bushing and having an annular flange at one end and, spaced from said one end, a portion of increased outer diameter projecting beyond said guide bushing and provided on its free end with an inner conical face; a lead receiving tube axially guided in said tubular clamping member; a collet connected at one end to said lead receiving tube and having at the other end thereof an outer conical face adapted to cooperate with said inner conical face for clamping a lead in said collet; a tubular slide member guided on its inner surface on the outer surface of said portion of increased diameter and, on its outer surface, on the inner surface of said tubular housing means, said tubular slide member projecting with one end beyond one end of said housing means; a lead supporting tube carried by said slide member and projecting beyond said one end of the latter; an actuating member projecting beyond the other end of said housing means and connected with said lead receiving tube for movement with the same in axial direction; and a single biasing means biasing said actuating member in a direction so as to cause engagement between said outer conical face of said collet with the inner conical face on said tubular clamping member, said biasing means being the only biasing means of said pencil.

2. A mechanical pencil as defined in claim 1, wherein said biasing means comprises a compression spring about said lead receiving tube and abutting with opposite ends against one end face of said guide bushing and said actuating means.

3. A mechanical pencil as defined in claim 1, wherein said tubular clamping member is provided in the region of said one end thereof with a plurality of axially extending slots extending also through said flange so that said flange may be compressed to an outer diameter smaller than the inner diameter of said guide bushing for assembling said tubular clamping member with said guide bushing.

4. A mechanical pencil as defined in claim 1, wherein said portion of increased diameter of said tubular clamping member forms with the remainder thereof a shoulder, said shoulder and said annular flange cooperating with opposite end faces of said guide bushing for limiting axial movement of said tubular clamping member in one and in the opposite direction.

5. A mechanical pencil as defined in claim ,4, wherein said housing means comprises a front part and a rear part alighned along a common axis, said parts abutting with adjacent ends against each other and being formed in the region of said adjacent ends with inner screw threads, said gude bushing being formed with an outer screw thread threadingly engaged with the inner screw threads of said parts to thus connect the latter to each other.

6. A mechanical pencil as defined in claim 5, wherein said guide bushing has a non-threaded axial extension engaging an annular inner surface portion of said front part with a close fit.

. 7. A mechanical pencil as defined in claim 1, wherein said housing means has adjacent said one end thereof an internal annular shoulder and wherein said slide member has at the other end thereof an annular flange adapted to engage said annular shoulder to limit outward movement of said slide member.

8. A mechanical pencil as defined in claim 1, and including a friction ring carried by said slide member axially aligned with said lead support tube for frictionally engaging a portion of a lead between said collet and said lead support tube. 

1. A mechanical pencil, especially for thin leads, comprising, in combination, elongated tubular housing means; a guide bushing in said housing means; a tubular clamping member axially guided in said bushing and having an annular flange at one end and, spaced from said one end, a portion of increased outer diameter projecting beyond said guide bushing and provided on its free end with an inner conical face; a lead receiving tube axially guided in said tubular clamping member; a collet connected at one end to said lead receiving tube and having at the other end thereof an outer conical face adapted to cooperate with said inner conical face for clamping a lead in said collet; a tubular slide member guided on its inner surface on the outer surface of said portion of increased diameter and, on its outer surface, on the inner surface of said tubular housing means, said tubular slide member projecting with one end beyond one end of said housing means; a lead supporting tube carried by said slide member and projecting beyond said one end of the latter; an actuating member projecting beyond the other end of said housing means and connected with said lead receiving tube for movement with the same in axial direction; and a single biasing means biasing said actuating member in a direction so as to cause engagement between said outer conical face of said collet with the inner conical face on said tubular clamping member, said biasing means being the only biasing means of said pencil.
 2. A mechanical pencil as defined in claim 1, wherein said biasing means comprises a compression spring about said lead receiving tube and abutting with opposite ends against one end face of said guide bushing and said actuating means.
 3. A mechanical pencil as defined in claim 1, wherein said tubular clamping member is provided in the region of said one end thereof with a plurality of axially extending slots extending also through said flange so that said flange may be compressed to an outer diameter smaller than the inner diameter of said guide bushing for assembling said tubular clamping member with said guide bushing.
 4. A mechanical pencil as defined in claim 1, wherein said portion of increased diameter of said tubular clamping member forms with the remainder thereof a shoulder, said shoulder and said annular flange cooperating with opposite end faces of said guide bushing for limiting axial movement of said tubular clamping member in one and in the opposite direction.
 5. A mechanical pencil as defined in claim 4, wherein said housing means comprises a front part and a rear part alighned along a common axis, said parts abutting with adjacent ends against each other and being formed in the region of said adjacent ends with inner screw threads, said gude bushing being formed with an outer screw thread threadingly engaged with the inner screw threads of said parts to thus connect the latter to each other.
 6. A mechanical pencil as defined in claim 5, wherein said guide bushing has a non-threaded axial extension engaging an annular inner surface portion of said front part with a close fit.
 7. A mechanical pencil as defined in claim 1, wherein said housing means has adjacent said one end thereof an internal annular shoulder and wherein said slide member has at the other end thereof an annular flange adapted to engage said annular shoulder to limit outward movement of said slide member.
 8. A mechanical pencil as defined in claim 1, and including a friction ring carried by said slide member axially aligned with said lead support tube for frictionally engaging a portion of a lead between said collet and said lead support tube. 